Social housing reduces anxiety in zebrafish


A new University of Liverpool study has shown that group housed zebrafish show lower levels of stress and anxiety when they undergo stressful or painful procedures like fin clipping than those who are housed singly. The research, funded by the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) and was recently published in Animal Behaviour.

Increasing numbers of fish are being used in scientific studies, and evidence is growing to show that fish experience stress and respond to pain with mechanisms comparable to mammals. Enriched tanks have been shown to reduce anxiety in fish, and housing in social groups is considered crucial for gregarious fish such as zebrafish (Danio rerio).

Analysing stress

Led by Dr Lynne Sneddon from the University’s Institute of Integrative Biology, this study compared recovery from common laboratory procedures (anaesthesia and fin clipping) in male zebrafish (AB strain) housed individually, in pairs and in groups of six. The team analysed responses which have been established as valid markers of stress, such as erratic movement, time spent at the bottom of the tank and stress hormone (cortisol) levels.

Anaesthesia alone and anaesthesia with fin clipping both had a significant impact on individually housed zebrafish, with these fish showing increased stress and behavioural alterations. The responses of zebrafish housed in groups was less pronounced, with group housed fish resuming normal behaviour more quickly than individuals or pairs, and showing the lowest cortisol increase.

During the study the researchers, based at the Universities of Liverpool and Chester, also validated the use of water-borne cortisol siphoned from tanks as an accurate and non-invasive measure of physiological stress. This method avoids the need for terminal sampling for measurement of whole body cortisol, helping to reduce the number of fish required for time series studies on physiological stress.

Research led teaching

The work was carried out by BSc Zoology graduate, Lewis White, who conducted his undergraduate Honours project in Dr Sneddon’s laboratory. Following graduation he went on to complete an MRes at Liverpool and is now embarking on a PhD at the University of York.

Read the research paper: 

Learn more about research led teaching at the University’s School of Life Sciences   

This adapted article was originally published on the NC3Rs website. Read the original article.


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